My vote would be none of the above.

Trail Dusters are indeed uber rare compared to Ram Chargers but I've never bought in to that making them more valuable. I mean the differences aren't more than a few badges. It's hard to argue against an as shipped 4x4 unless it's got the 318 and ya have no use for the 4wd. I've never been a fan of laying frame or much of a drag racer so those options aren't my cup of tea.

I'd go basic big block 2wd street terror. I've got an LRE and it's a lot more fun on twisty roads than my 318 4wd RC but it's not a convertible. The G3 Hemi swap is the current big thing - to the point that Holley is actually making kits for it. It's "only" 3-5x the cost of vintage iron. Tempting but ya know, a couple 440s in the basement.

As for 4wd to 2wd, no need to cut frame rails if your parts donor is a 72-93 pick-up. Just swap the engine cross member and upper control arm mounts and then move the rest of the front suspension over. I'm pretty sure they left both sets of mounting holes (small block vs big block) in the cross member through the end of the run. Another good trick is find the much more common 2wd RC from the 80s and swap tubs. There is a difference in the frames because they added rear seat leg room when getting rid of the pop top but you can get around it with different height body mount bushings.